a) Technical Field
The present invention relates to a motor. More specifically, it relates to the technology of thinning the casing of the (stepping) motor.
b) Description of the Related Art
FIGS. 1(A) and (B) illustrate a compact stepping motor 1 for use in a digital camera, digital video camera, and slim optical disk drive (ODD). Stepping motor 1 is generally constructed in the following manner: a circular first bobbin 5A wrapped with a coil and a second bobbin 5B (also wrapped with a coil) abut each other in the motor's axial direction; and a rotor securing hole is provided by first bobbin 5A and second bobbin 5B such that multiple poles of inner stators 2A, 2B and outer stators 3A, 3B are circumferentially arranged. Rotor 7 is secured around rotary shaft 71 fitted with rotor magnet 72. Rotor magnet 72, secured on the rotor securing hole, faces stator poles over a given space therebetween. Plate 8 is secured onto outer stator 3B to hold thrust bearing 82 which supports rotary shaft 71. Alternately, radial bearing 81, which is supported by plate 8, may support rotary shaft 71 as shown by the dotted line in FIG. 1A. Rotary shaft 71 is further supported by thrust bearing 82 arranged toward the first bobbin 5A end. Thrust bearing 82 is pressed against rotary shaft 71 by flat spring 83, which is cut and raised at the bottom of metallic cup-like cover 80 bonded to outer stator 3A. Terminals 50A, 50B are provided at the outer end of first bobbin 5A and second bobbin 5B in a radial direction such that the ends of the coils are terminated at terminal pins 51A, 51B of terminals 50A, and 50B. The circumferences of outer stators 3A, 3B constitute casing 2; and terminals 51A, 50B project through openings on casing 2.
Stepping motor 1 as configured above has cylindrical casing 2 whose cross section in a direction perpendicular to the plane of the motor axis is truly circular.